Overview:
Chemical formulas are abbreviations for chemical compounds. They contain both the elements in the compound and the ratio of elements to one another. They are used as shorthand to describe chemical reactions.
How Are the Elements Symbolized?
The name of each element in the periodic table is abbreviated so that each element has its own symbol. Fourteen elements have a one-letter symbol, such as hydrogen (H), carbon (C), fluorine (F), and sulfur (S). Six elements have unofficial three-letter symbols, and the rest have two letter names, such as helium (He), aluminum (Al), and chlorine (Cl).
Why Don’t All the Symbols Make Sense?
Some elements have symbols that derive from early names for them, such as gold (Au), silver (Ag), potassium (K), and lead (Pb). The names were in Latin, and many of the names were used by the alchemists, who had their own set of symbols for common elements, processes, mixtures, and compounds, such as sugar, glass, and nitric acid.
What Are Some Compounds with Elements in an Equal Ratio?
Many compounds have elements in an equal ratio to one another. For example, common table salt (NaCl) has one sodium atom for one chlorine atom in every molecule. Similarly, carbon monoxide (CO) has one carbon atom for one oxygen atom in every molecule. Hydrogen chloride (HCl) also has one atom of hydrogen with one atom of chlorine in each molecule of the compound.
What Are Some Compounds with Elements in an Unequal Ratio?
Many compounds have elements in an unequal ratio to one another. The number of atoms is indicated in a subscript to show how many atoms there are in a molecule. For example, H2O, the formula for water, states that there are 2 atoms of hydrogen for every atom of hydrogen in a molecule of water. The chemical formula for sodium nitrate is NaNO3, standing for one atom of sodium, one of nitrogen, and three of oxygen. If a group of atoms occur in a unit within a molecule, parentheses are placed around the group. For example, the chemical symbol for calcium nitrate is Ca(NO3)2, which states that there are two nitrate groups for every atom of calcium within a molecule.
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